RESEARCH LETTERS converged toward the same result: the convalescent- SARS-CoV-2 in Quarantined phase serum from the cat contained immunoglobu- lins against SARS-CoV-2, which were absent from Domestic Cats from the serum from control cats. These antibodies target COVID-19 Households several distinct viral proteins, and they caused a total or Close Contacts, neutralizing effect up to a much higher dilution than those from the owner’s serum. This household cat Hong Kong, China was therefore productively infected with the SARS- CoV-2 virus excreted by its owner, and the infection Vanessa R. Barrs,1 Malik Peiris,1 Karina W.S. caused a nonfatal but nevertheless severe disease, Tam, Pierra Y.T. Law, Christopher J. Brackman, mainly of the respiratory system (Videos 2–6). Esther M.W. To, Veronica Y.T. Yu, Daniel K.W. Chu, Public health officials are still learning about Ranawaka A.P.M. Perera, Thomas H.C. Sit SARS-CoV-2, but no current evidence indicates that pets play a role in spreading the virus. Therefore, tak- Author affiliations: City University of Hong Kong, Hong Kong, ing measures against companion animals that may China (V.R. Barrs); The University of Hong Kong, Hong Kong (M. compromise their welfare is not justified. Peiris, D.K.W. Chu, R.A.P.M. Perera); Government of the Hong Kong Special Administrative Region, Hong Kong (K.W.S. Tam, P.Y.T. Law, C.J. Brackman, E.M.W. To, V.Y.T. Yu, T.H.C. Sit) Acknowledgments We thank Emmanuel Vidal and Sébastien Quesney for DOI: https://doi.org/10.3201/eid2612.202786 serologic testing. In addition, in alphabetical order, we thank K.-Y. Chen, C. Demeret, M. Franssen, We tested 50 cats from coronavirus disease households or and S. Temmam for their interventions in various close contacts in Hong Kong, China, for severe acute re- spiratory syndrome coronavirus 2 RNA in respiratory and capacities in the establishment of molecular and fecal samples. We found 6 cases of apparent human-to- serologic diagnostics. feline transmission involving healthy cats. Virus genomes sequenced from 1 cat and its owner were identical. About the Author aturally occurring human-to-animal trans- Prof. Garigliany is a senior researcher and professor of mission of severe acute respiratory syndrome General and Molecular Pathology at Liège University, N (SARS) coronavirus was reported during 2003 when Belgium. His primary research interests include host– viral RNA was detected in oropharyngeal and rec- pathogen interactions between animals and RNA viruses. tal swab specimens from healthy domestic cats in a housing estate at the center of a large SARS cluster Reference in Hong Kong, China; infections were confirmed se- 1. ProMED-mail. COVID-19 update (58): Belgium, animal, cat, rologically (1). Susceptibility of cats to infection with clinical case, RFI. 2020 May 20 [cited 2020 Jul 31]. this virus and transmission between cats were dem- http://www.promedmail.org, archive no. 20200327.7151215 onstrated experimentally (2). Pulmonary pathologic changes, similar to those for humans with SARS, Address for correspondence: Daniel Desmecht, University developed in infected cats, but the cats remained as- of Liège, Faculty of Veterinary Medicine, Department of ymptomatic (2,3). Pathology, Sart Tilman B43, 4000 Liège, Belgium; email: These findings informed the current precaution- [email protected] ary strategy of the Agriculture, Fisheries and Con- servation Department of Hong Kong to quarantine mammalian pets from households with confirmed human coronavirus disease (COVID-19) or their close contacts (defined as a person who had face- to-face contact for >15 min with a person who had confirmed SARS Coronavirus-2 [SARS-CoV-2] in- fection) in a holding facility, when alternative care was unavailable. Pets are swabbed for SARS-CoV-2 testing and confined until reverse transcription PCR (RT-PCR) results are negative on 2 consecutive oc- 1These authors contributed equally to this article. Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 26, No. 12, December 2020 3071 RESEARCH LETTERS casions. Findings for 2 infected dogs have been re- Fisheries and Conservation Department Veterinary ported (4). We report testing results for cats. Laboratory by using a commercial RT-PCR target- Swab (nasal, oral, rectal) specimens and feces ing the partial envelope and RNA-dependent RNA collected from nonsedated cats after admission were polymerase genes (Molbiol Lightmix; TIB MOLBIOL, tested for SARS-CoV-2 RNA at the Agriculture, https://www.tib-molbiol.com). This PCR does not Figure. Phylogenetic analysis of SARS-CoV-2 full genome from an infected cat and the human index case-patient, Hong Kong, China. A virus sequenced directly from a tiger in a zoo in United States was included in this analysis. Virus genome alignment was prepared and manually trimmed at genome 5′ and 3′ ends for low-alignment quality. A resulting alignment of 29,655 nt was analyzed by using PhyML (http://www. atgc-montpellier.fr) and the generalized time reversible nucleotide substitution model. Branch support identified by using the fast approximate likelihood ratio test are shown at major nodes. The Hong Kong feline virus from cat 1 and that of its owner are shown in red. Canine and human viruses from Hong Kong, including from the dogs’ owners (HK_case 163 and HK_case 85) are shown in blue. Numbers along branches are bootstrap values. Scale bar indicates nucleotide substitutions per site. SARS-CoV-2, severe acute respiratory syndrome coronavirus 2. 3072 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 26, No. 12, December 2020 RESEARCH LETTERS show cross-reactivity with these genes from enteric known for 3 cats (5, 11, and 8 days); 1 had equivo- coronavirus (5). cal envelope gene PCR results but was positive by a For samples with positive or equivocal results, novel surrogate virus neutralization test (6). Signs of confirmatory quantitative RT-PCRs targeting non- disease did not develop in any infected cats, consis- structural protein 4, nonstructural protein 16, nu- tent with experimental feline infections, which are cleoprotein, and membrane genes were performed at also usually subclinical (7; A. Bosco-Lauth et al., un- the World Health Organization COVID-19 Reference pub. data). Laboratory at the University of Hong Kong (4). Ani- COVID-19–like signs have been reported in do- mals with positive results were evaluated by repeated mestic cats naturally infected with SARS-CoV-2 in oth- sampling to monitor viral shedding by RT-PCR. Sero- er countries (8). In addition, 4 tigers and 3 lions with logic analysis was used selectively. respiratory signs in a zoo in New York, New York, We sampled 50 cats during February 11–August USA, were confirmed to be shedding SARS-CoV-2 in 11, 2020. Time from onset of COVID-19 symptoms in feces (S.L. Bartlett et al., unpub. data). Susceptibility to owners to first sampling of their cats was available for SARS-CoV-2 might differ between felid species. 21 owners of 35 cats and ranged from 3 to 15 (median 8, SARS-CoV-2 RNA persisted longest in nasal se- interquartile range 4) days. SARS-CoV-2 RNA was de- cretions in 1 case for 11 days at low levels. Viral RNA tected in samples from 6 (12%) of 50 cats (Table, https:// was detected in nasal washes from kittens experimen- wwwnc.cdc.gov/EID/article/26/12/20-2786-T1.htm). tally inoculated with SARS-CoV-2 for 8–9 days, after The first positive case (cat 1) was from a house- which sampling was stopped (7). Cats acquiring in- hold that had 3 persons with confirmed cases of CO- fection from being cohoused with experimentally in- VID-19; their symptoms (fever, cough, or shortness of fected cats shed virus in respiratory secretions longer breath) started on March 20, 29, and 30, 2020. Their (7 days) than directly inoculated cats (5 days) (8). 7-year old, female, domestic shorthair cat was exam- Although feline-to-human transmission is theo- ined by a veterinarian at admission on day 1 (March retically possible, we did not find any evidence of this 30), and reported to be clinically healthy. Nasal, oral, transmission. The timeline of infection in cat 1 and the and rectal swab specimens collected on day 1 were finding of an identical SARS-CoV-2 genome sequence positive for SARS-CoV-2 RNA; viral nucleoprotein in a human from the same household is consistent gene copy numbers were log10 6.3/mL, log10 5.6/mL, with human-to-animal transmission. In support of and 3.2 log10/mL, respectively. these findings, the cat had no outdoor access. Attempts to culture virus from day 1 samples on More widespread serologic surveillance of cats in Vero E6 (ATCC CRL-1586) cells as described (4) were contact with COVID-19 patients is warranted to de- unsuccessful. Viral RNA was detected in oral swab termine the prevalence of human-to-cat transmission. specimens for 8 days and nasal swab specimens for 11 Some infected cats might have stopped shedding vi- days, but rectal swab specimens were negative after rus before being quarantined because viral shedding day 1 (Table). periods as short as 3 days have been reported in ex- We performed serologic analysis to detect neu- perimentally infected cats (7). tralizing antibodies by using a 90% plaque reduction neutralization test for SARS-CoV-2 (4). The result was Acknowledgment positive for the only serum sample collected (on day We thank Dominic N.C. Tsang for providing the human 19) and had titer >1:320 (4). specimen. Viral genomes from cat 1 and 1 owner were se- quenced by using a MiSeq Sequencing Platform (Il- M.P. was supported by the US National Institutes of lumina, https://www.illumina.com) after reverse Health (contract no.